Modern medicine : its theory and practice, in original contributions by American and foreign authors . of the bron-chial stricture. Pathogenesis.—There ismuch difference of opinionas to the mode of production of bronchial dilatation, but all are agreedthat the affection is a secondary one. It is generally preceded by chronicdisease of the dilated bronchus, and associated with this there is, as a rule,sclerosis of the lung and pleura. The various opinions as to the mechanism of dilatation may be groupedinto two classes: 1. Those which regard the causes acting within the bronchi as playingthe pr
Modern medicine : its theory and practice, in original contributions by American and foreign authors . of the bron-chial stricture. Pathogenesis.—There ismuch difference of opinionas to the mode of production of bronchial dilatation, but all are agreedthat the affection is a secondary one. It is generally preceded by chronicdisease of the dilated bronchus, and associated with this there is, as a rule,sclerosis of the lung and pleura. The various opinions as to the mechanism of dilatation may be groupedinto two classes: 1. Those which regard the causes acting within the bronchi as playingthe principal or essential role. 2. Those which regard lesions external to the bronchi (a) of the lungsand (6) of the pleura, as taking a part in causing the dilatation. Some observers regard all three classes of causes as acting unitedly toproduce the bronchial dilatation. 1. Causes Acting within the Bronchi.—The view which is generally adoptedto account for the dilatation of the bronchi rests upon two principal factors:(a) lesions in the bronchial wall by which its power of resistance to pressure. Microscopic section of Fig. 30, (Transactions of the Patho-logical Society of London, vol. liii.) BRONCHIECTASIS 685 is diminished, and (b) increase in the intrabronchial pressure by expiratoryeffort, with partial or complete closure of the glottis, especially in coughing,but also in crying and singing. The expiratory pressure of cough may easily rise to 80 mm. of mercury,and in severe coughing 110 or more may be reached; in quiet expiration itdoes not exceed 2 or 3 mm. This shows the very great variations of pressureto which the respiratory tract may be subjected. Violent cough mustalways cause distention of the bronchi and may appreciably increase theircaliber, from which the elastic and muscular tissues in health cause animmediate recoil. Such sudden increase of pressure is the common causeof emphysema; weakened parts of the bronchial tree must yield under sim-ilar circumstances if
Size: 1589px × 1573px
Photo credit: © The Reading Room / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookcentury1900, bookdecade1900, booksubject, booksubjectmedicine
